Continuous tinplate brightening apparatus



Jan. 18, 1949. s, NACHTMAN 2,459,674

CONTINUOUS TINPLATE BRIGHTENING APPARATUS IL, INVENTOR Jan. 18, 1949. Y J. s. NACHTMAN 2,459,674

CONTINUOUS TINPLATE BRIGHTENING APPARATUS Figa lNjf/ENTOR Jan. 18, 1949. J, 5 NACHTMAN 2,459,674

CONTINUOUS TINPLATE BRIGHTENING APPARATUS Filed Dec. 30, 1939 4 Sheets-Sheet 3 INVENTOR in w.

Jam 18, 1949- J. s. NACHTMAN CONTINUOUS TINPLATE BRIGHTENING APPARATUS 4 Sheets-Sheet 4 Filed Dec. 30, 1939 Ratented 108, 19.49

CONTINUOUS sV PATE TINPLATE APPARATU N1"v oFiFlcE. A

mIGH'rENING John AS. Nachtmameaver, Pa. Application December 30, 1939, Serial No. 311,929 14 claims. (ci. ass-3) The present invention relates-tc apparatus for applying a nishing treatment-although not necessarily the nal treatment-to coated strip metal such as a sheet metal base carrying a film or layer of metal, e. g., electrodeposited metal, on a surface thereof. This application is a continuation-impart of apparatus subject-matter of my copending applications, Serial No.v 133,911, ied March 30, 1937, now Patent No. 2,240,265, granted April 29, 1941; Serial No. 206,257, iiied Mayl 5, 1938, now Patent No. 2,357,126, granted August 29, 1944; Serial No. 257,107, filed May 18,

1939,-:now abandoned; Serial No. 279,866, filed June 19, 1939; and Serial No. 675,897, iiled June 11, 1946.

` The common hot-dip method involving, for example, the application of tin to strip steel, produces a coating generally poor in quality both as to uniformity and appearance. Electrodeposi- -tion alone, particularlyl in continuous high-speed I"strength of union or adherence of coatingto base l metal is too low. This problem is increased Where processes, tends to produce a coating which, while having a better appearance and an nnproved uniformity, has localized areas wherein the line for suitably proportioning the tension, speed I and rate of treatment of the material, particularly while continuously moving the material through the line.

Such a control of tension in the line avoids objections encountered heretofore in the apparatus used. I discovered that in plating of extremely thin strips or :tlne wires at relatively high speeds, there was a progressively building up of tension inthe strip, and that this building up was particularly great in the case of a long plating line which was required of course in'connection with high speed operation. High as well as unsuitable tension of the strip being treated, as well as "surging in the line, not only tend to distort the strip but also to spoil the plating operation and" the coating provided thereby. I discovered that there are a number of factors involved in electroplating from the standpoint of conveying or moving the strip continuously past or through the necessary treatment zones that entered into the characteristics of the product, as well as the 5 effectiveness of the individual and collective treatments.

I determined also that it is important that the elimination of tension surges and the maintaining of proper tension in the line produced a l0 more or uniform deposit of metal on the strip and a better and brighter appearance resulting from-"the brightening operation.

.This desired control of tension may be provided in various ways as set forth more in de- 16 tail in my above-mentioned prior applications, particularly in the application for my patent, No.

2,240,265, granted April 29, 1941, and in my application, Serial No. 257,107, now abandoned, iled 'February 18, 1939. For instance, it is preferred 20 thatl provisions be made at various points in the line to move the strip continuously through the linepand through the various operations thereof at a suitable 'speed and under the desired tension. Such provisions may be by the driving of the guide rolls by motors that will operate the rolls in contact with the strip while preventing the undesirable building up of tension in the strip, or operating pinch rolls by motors in such manner as to provide a drag tension, or by the provision of dancer rolls at suitable points in the line, or these various elements may be combined according to the needs and requirements of the operation and the speed of the line.

The major objects of the present invention will be apparent from the preceding discussion. Further important objects reside in the provision of novel and useful iapparatus in several forms for effectively treating a strip of coated material in the manner set forth, and other objects will appear as the description proceeds. The drawings accompanying this specification consist of the following illustrations:

Figure 1 is a side elevational view, with portions of the supporting structure in section, of a preferred form of apparatus constituting a part of this invention;

Figure 2- represents a vertical section taken substantially on the plane of line 2-2,`Figure 1, looking in the direction of the arrows;

Figure 3 represents a further vertical section taken on a plane normalto that of Figure 2, substantially on the plane of line 3-3 of Figure 2, looking in the direction of the arrows;

t Figure 4 is a View similar to Figure 3, but show- 55 ing a somewhat modified form of apparatus;

l1 into said chamber.

ously through a series of treating apparatus (see Figs. 6a and 6b) and has lust come through a plating bath where it received, by electrodeposition, a surface coating of metal, e. g., of tin, all

as described in my application, Serial No. 133, 911,

now Patent No. 2,240,265. It is shown entering into, passing through and emerging from the brightening apparatus, indicatedl generally'and in its entirety by the numeral 3.

'I'he apparatus 3 has a shaping and supporting framework including vertical corner stanchions .9 intertied by cross members I0, the stanchions projecting downwardly into a pit I2 below a floor I3. This framework carries four vertical walls Il, properly joined andl sealed at their edges to form a rectangular tank closed at the bottom by a plate I5. The tank is substantially filled with liquid as indicated. and by means of a horizontal baille plate I6 and a vertical partition I1 the tank is divided into a pair of chambers I8 and I3, hereafter referred to respectively as the fusing and chilling chambers. The partition I1 is a hollow double-walled structure filled with a heat-insulating material 20. Q

The chambers I3 and I3 open upwardly into a hood 22 and have individual stack vents 23 and 2l, separated by the upper part of the partition I1. The vent 23 preferably is provided with a damper 25. Two of the hood walls, as shown (Fig. 3) are inclined to overhang two of the walls I3 and form therewith and with a pair of added vertical walls 26 and 21, a pair of chambers 23 and 29 hereafter referred to respectively as the pre-heating and exit chambers.l The walls 26 and 21 are approximately U`shaped in cross section, and the former is covered with heatinsulating material 33.

The bottom of chamber 23 is formed by a plat-l form 3l upon which is mounted a pair of entrance rolls 32 which pinch and feed the strip One of these rolls is driven by a motor 33 (Figure 2). The strip passes upwardly, centrally of the chamber 23, to a driven A guide roll 34, the latter being disposed within hood 22 and having a shaft 35 driven by a motor 36 and mounted in bearings 31. 'I'his guide roll is so located that the strip then passes downwardly centrally of the chamber I3 througha slot 33 in the baille I6 and thence to a second guide roll 39. The latter is journaled in bearings 4I) so disposed that the strip can be drawn off toward the center of the upper section of the chamber I3. Atop the chamber I3 and above the liquid level there is disposed a pair of rolls, l2, 43 (Fig. 3) which serves as a squeegee and guide assembly for the traveling strip. The strip preferably is then drawn downwardly toward floor levelto leave the apparatus by way of a delivery roll Il and thence either to be reeled or tobe passed on for further treatment. A platform I6 carries the roll M, and a shielding wall 21 preferably isi provided to protect the strip in its passage to said roll.

One of the walls I4 has a removable cover 41 for facilitating assembly, adjustment and repair of some of the parts.

As previously statedfthe preheating and fusing may be done in any manner suitable for obtaining the requisite temperatures. The illustrated embodiment of preheating means comprises two banks of electrical heating elements 43 varranged in the chamber 23 on opposite sides of the strip 1 and controlled by a thermostat I3 which is adjusted to afford a chamber temperature that will cause some alloying between the' coating metal and the steel without actually fusing the coating metal. If the coating material happens to be such as will oxidize readily, reducing gas may be injected into the preheating chamber or may be caused to pass from the hood above the fusion chamber I3 into the chamber 23 by closing the damper 26. In some cases, suflicient preheating temperatures are obtainable by `conduction through and radiation from the wall between the fusing and preheating chambers.

The liquid in the fusion chamber I3 may likewise be heated by banks of electrical units, I3, under the control `of oneor more thermostats 32 that are adjustedto afford a temperature that will cause the coating to fuse and iiow suiiiciently to spread uniformly and smoothly over the surface of the base metal; at the temperature of the fusion chamber the coating further alloys itself simultaneously with the base metal of the strip. The liquid heat-transmitting medium may consist of oil or oily medium with a sufliciently high flash point and no appreciable tendency to attack the metal coating.

The baille plate I3- tends to prevent liquid circulation and heat exchange between the chilling and fusion chambers. It minimizes the formation of eddy currents by the moving strip.

Almost immediately after passing the baille the strip 1 has its coating chilled and hardened by the impingement thereon of iets of cooling liquid which come from opposed sets of immersed pipes 53 designed to spray the cold liquid toward the two surfaces of the strip. 'Ihese pipes connect to manifolds or headers 34 externally of the chamber and the manifolds in .turn connect by way of a pipe 55 to the discharge side of a liquid cooling and circulating unit that comprises a pump 66 and a heat exchanger 31 '(Fig. 1). The exchanger has the usual connections 33, 63 for circulation therethrough of a separate heat removing liquid.

'I'he intake side of the pump I3 is designed to withdraw the heat-transmitting oil or other liquid from the chilling chamber I3, and, to eectively accomplish this, the withdrawal is effected at three points by means of a pipe 33 having branches 62, 63, the branch 63 in turn having a branch 64. Each branch is equipped with a valve, as shown, for manually regulating the flow through each and thus controlling the chamber temperatures at and adjacent the points where the branches enter the chamber.

The branch 62 enters the bottom of the chillin! chamber and is regulated to draw of! just enough liquid to insure constant mixture or internal circulation of the liquid. Branch 33 is connected to a manifold 35 from which a pair of pipes lz project into the chamber immediately adjaceny the baille I3. Best temperature conditions are obtained by removing most of the total withdrawn liquid through these pipes 33. The third branch, 34, Figure 1, terminates-in a pipe section 31 that is disposed in the extreme upper part of the chilling chamber (Figure 3). In some instances, where the heat-transmitting or chilling liquid is viscous it will be desirable to use this pipe section, or added heating elements adjacent thereto, to heat the surface portion of the liquid and renderit readily removable by the squeegee assembly l2, 43.

As shown in Figure 2, a chamber 68 containing a iloat 69 may be provided in communication with the upper part of the liquid body, with the float connected to an electrical switch device forthe purpose of maintaining the desired constant liquid level, in obvious manner, with the switch device in circuit with means governing the liquid supply. Obviously, the control for the heating units, 50, may be connected in this circuit so that the heat will be disconnected if liquid level falls too far. v

The mode of operation of the above described apparatus and the results obtained thereby in the several successive steps should now be well understood, and a detailed summary therefore is'- believed unnecessary. The preheating step hasl several functions as above set forth, but its primary purpose is to bring the entire strip to a temperature approaching but short of the fusion temperature of the coating, thus permitting the fusion chamber to be of a desirably short length. The vertical stretch of the strip is preferable for passage through the fusion chamber as it aids in. producing a rapid and uniform spreading of -the fused metal, and supports the strip without tendency to distort or to deflect. Hence the slot 38 in the baille may be of a. desirable mini-mum width. During the interval between contacting driven guide roll 34 and contacting roll 39 the coated strip does not contact any solid object: in that interval the already preheated coating is brought to fusion temperature and then is solidied, solidication being complete before the coated strip reaches roll 39. Preferably, the procedure is so effected that actual melting of the coating occurs by the time the strip approaches the bottom of chamber I8, thereby makingthe interval of actual molten condition of the coating an extremely brief one. This is desirable because if the coating is maintained at or above melting temperature too long there is a tendency for the depth of coating to become less uniform than otherwise.

The heating and cooling arrangements o f Figures 1 to 3 are important, but may be modified somewhat within the scope of this invention. For example, the liquid medium may be omitted partially or entirely. Figure 4 illustrates a modification where it may be completelyA eliminated. In describing this form no specific reference will be made to those parts which are duplicates of some of those in Figure 3.

The major change in Figure 4 consists in re-` moval of the upper section of the chilling chamber and its squeegee assembly and in withdrawal of the strip directly from the top of the shortened chamber. In doing this, the hood is narrowed to aord a suitable hood 22a having an intake pipe 23a., and a shortened wall structure -I 4a is substituted for three of the walls M of Figures 1 to 3. The partition |1a and its insulating material 20a are brought downwardly into proximity to. the lower guide roll 39, for efciency in chilling by gas in the chamber l 9a. I'he deliveryV roll 44 is mounted on the wall structure to receive the strip direct from the roll 39 since the soueegee action isunnecessary where gas is used for the chilling purpose.

The sets of heating. elements (la, disposed in the preheating chamber and controlled by the thermostat 49a, preferably consist of gas .iets which burn with reducing flames directed against the strip surfaces. This is true also of the heating elements 50a of the fusion chamber I8 under control of thermostats. 52a. If a reducing atmosphere is desirable, and not sufficiently provided by the gas jets, reducing gasesv may be injected into the heating chambers through the hood pipe 23a. The injected gases may be suiilciently hot for preheating, and hence need to be augmented only by fusing elements in the chamber I8. It is of course -to be understood that the temperatures and their relationship to each other and the fusion point of the strip coating-'must be maintained Aas previously set forth in the objects and in the description of Figures 1 to 3.

Although liquid may be used for cooling in conjunction with gaseous heating, the chilling apparatus of Figure 4 is designed to operate through a gaseous cooling medium, such as cold air, cold neutral gas or cold reducing atmosphere-preferably a cold reducing atmosphere. To this end the pipes 53a receive the cold gas under pressure and discharge it in jet form against the strip. Circulation is maintained by withdrawing the warmer gas through the pipe sections 66a, any suitable pumping and heat-exchanging apparatus being connected to pipes 53a and 66a externally of the chamber in obvious manner.

By filling the chilling chamber with liquid to a level just below the baille I6, and substituting a pair of squeegee rolls for the delivery roll Il, a liquid cooling .medium such as cold oil, or cold water, may be circulated through the pipes 53a and 66a in lieu of the cold reducing atmosphere.

In Figure 5 there is illustrated a further modification, having the same three major parts as the preceding forms but' having said parts rearhaving one side inclined to the horizontal in a direction upwardly and away from the tank 12". An inclined tube 14 which is rectangular in cross section joins the two chambers, both of which are filled with liquid to the indicated level, maintained by the float-switch device 69, 1o in conjunction with any suitable supply means. The tanks have normally closed drain pipes 15, 16.

The upper end of the preheatingr tank has a slot 11- for the entrance of the strip 1 from the feeding rolls 32h.` From these rolls the strip passes downwardly to the guide roll 34h and then is drawn oil at an angle through the tube 14, the fusion tank and the baille |612 by a pair of squeegee rolls 42h, 43h. The latter are located adjacent the strip outlet side of a chilling tank 18, which at said outlet side has a baille 'I9 through which the treated strip is discharged.

The liquid is preheated in the tank 'I2 by elements 48h that may comprise hot pipes but which preferably consist of electrical units controlled by a thermostat 49h. Likewise the units 50h in the fusion tank may take various forms but preferably comprise electrical elements under con- :andere 7 trol oi a thermostat 52h. A vent pipe 80 serves to remove hot vapors and gases adjacent the baille IIb, thus minimizingthe heat transfer between the fusion and chilling chambers.

The strip is quickly chilled in the tank 1l by jets of cold air, cold 'neutral gas or cold reducing gas, preferably lfed against it from pipes 53h. A withdrawal pipe 82 at a higher point in the tank serves to return the warmer gas to the coolof tin,`they may, withoutl the exercise of inven- 4 tive genius, beemployed foi` a like treatment of other metallic coatings and for combinations in which the base metal is other than steel. Thus,

' the process and apparatus are operable for like treatment of metallic strip material carrying a coating of copper, or zinc, or nickel, or lead, or bismuth, or other metal which has a melting point lower than the melting point of the base metal, or copper and zinc,- or copper and tin, or nickel and copper, or lead and tin, or lead and bismuth, or any other combination of two coating metals the outermost of which shall have a melting point below the melting point of the base metal. Like- Iwise, they are operable for treating metal-coated strips whose base lmetal iscopper, aluminum, nickel, stainless-steel, Monel metal or any other metal strip having a higher melting temperature than that of the exposed coating metal.

With reference to the specific combination hereinbefore referred to, of strip steel of relatively lowV carbon content and of about A30 guage.

to about 150 F. or below before being contacted by any solid object.

The process described above in connection with the apparatus shown in Figs. 1 to 5, is claimed in my prior patent, No. 2,357,126.

While the invention has beenspeciilcally described hereinbefore with particular reference to the treatment of electrically deposited metalliccoatings, it is to beappreciated that the process and apparatus of the invention4 are applicable, without inventive change, to the treatment of coatings which have been applied by the known hot dip method. It will appear, for example,

Itwill also appear that the term strip as employed herein applies to any suitable base metal preferably having some nexibility to permit it to be interleaved overv or between suitable rolls.

As illustrated and described in my cepending. applications, Serial No. 133,911 (now patent,

No. 2,240,265) and Serial No. 2573107, now abandoned, the electroplating line through which the strip passes, includes means for subiectingthe strip to tensioning actions during passage through the line, as shown in Figs. 6a and 6b, as an example, substantially as illustrated in the aforesaid patent. No. 2,240,265. As here shown, the 'strip 1 is fed from a pay-out device A, through a welding device B, where successive lengths of strips are joined together in continuous fashion. A pressure device or squeegee C is provided for aligning and tensioning of the strip, from which the strip passes to a slack producer D, thence to squeegee rolls C. The strip is then directed into la cleaning tank F, and through a scrubbing mechanism G, rinse tank H and pickle tank I. to another scrubbing mechanism G'. From the 'scrubbing mechanism G', the strip is directed through a bridle stand J, around a weighted` dancer roll J', to an electroplating tank K. From the electroplating tank K, the strip 1 is again scrubbed at` G2, and passes into a rinse tank L, and a hot air drier M.

After leaving the drier M, the yplated stockis subjected to the tensioning action of a weighted dancer roll 80', and th'en passes into the brightening apparatus generally indicated at N, as described above and illustrated in Figs. 1 to 5. Not only do the dancer rolls control the tension in the strip 1, but also the tension is controlled by the bridle stand J and dancer-roll J I as described more in detail in my prior application. Serial No. 133,911 (Patent No. 2,240,265).

Moreover, set forth in lmy p rior application, Serial No. 257,107, -flled February 18, 1939,v now abandoned, the squeegee rolls C and C'. and other power-drive guide rolls for controlling the move- -ment of the strip through theline, have a maelectric motors which will operate these at thedesired speeds to tension the strip properly through the treating operations and to eliminate line surges that arise particularly in along line pinch roll motor, as well as the bridle stand motor,

may serve to provide a drag tension which -fur ther aids `in maintaining the desired tension in the line, all as' set forth more in detail in my prior application referred to and in my patent mentioned above.

that the coated strip may be fused and heat-conditioned by heating it to altemperature below the Y .melting point of the coating (such as tinl and by Obviously, many other alterations and rear-y rangements of parts in the several illustrated forms may be made without departing from the spirit and scope of the inventionwhich maybe determined from the appended claims. y

I claim:

1. In apparatus for treating electroplated coatings on continuous metal strip, means for preheating the strip to a temperature below the fusing temperature of the coating thereon, separate means for briey heating the coating to a fusing temperature, separate means for quickly solidi-- tying the coating, means for continuously moving The ,the strip under tension and means for controlling the tension in the strip through the apparatus, whereby a uniform smooth bright tin surface is provided on the strip.

2. In apparatus for treating electroplated coatings on continuous metal strip, means for pres heating the strip to a temperature below the fusing temperature of the coating thereon, separate means for briefly heating the coating to a fusing temperature, separate means for quickly solidifying the coating under non-oxidizing conditions and loca-ted substantially vertically below the last-mentioned heating means, means for continuously moving the strip under tension, and a roll acting on the strip during movement through the apparatus in a direction for controlling the tension in the strip therethrough whereby a uniform smooth bright tin surface is provided on the strip.

3. In apparatus for treating electroplated coatings on continuous metal strip, means for preheating the strip -to a temperature below the fusing temperature of the coating thereon, separate means for briefly heating the coating under -separate means for quickly solidifying the coating under non-oxidizing conditions and located substantially vertically below said last-mentioned heating means, means for continuously moving the strip under tension through said preheating, heating and solidifying means and lncluding guide means for the strip arranged in position out of -contact with the fused portion of the strip, and a roll acting on the strip during movement through the apparatus in a direction for controlling the tension in the strip therethrough whereby a uniform .smooth bright tin surface is provided on the strip.

5. In apparatus for treating electroplated coatings on continuous metal strip, means for heating the coating to a fusing temperature, means for solidifying the coating, means for continuously moving the strip under tension and means for controlling the tension in the strip through the apparatus, whereby a uniform smooth bright tin surface is provided on the strip.

6. In apparatus for treating electroplated coatings on a continuous metal strip,v means forming respectively heating and quenching zones and including means for heating the coating in the heating zone to a fusing temperature and means for solidifying the coating in the quenching zone, said quenching zone being located below the heating zone for downward movement of the strip in a substantially vertical path from the heating zone to the quenching zone, means for continuously moving the strip under tension through said zones including means for guiding said strip through said path and arranged in position out of contact with the fused portion of l the strip, and roll means for controlling the tension in the strip through the apparatus whereby '1. In apparatus for treating electroplated coatings on a continuous metal strip, means forming respectively heating and quenching zones and including means lfor heating the coating in the heating zone under non-oxidizing conditions to a fusing temperature and means for solidifying the coating under non-oxidizing conditions in the quenching zone, saidquenching zone being located below the heating zone for downward movement of the strip in a substantially vertical path from the heating zone to the quenching zone, means for continuously moving the strip under tension through said zones including means for guiding said strip through said path and arranged in position out of contact with the fused portion of the strip, and power-operated rolls acting on the strip during movement through the apparatus for controlling the tension in the strip therethrough whereby a uniform smooth bright tin surface is provided on the strip.

8. In apparatus for treating an electroplated coating on continuous metal strip, meansfor heating the -coating to a fusing temperature, means for thereafter solidifying the coating, means for continuously moving the strip under tension through the apparatus, and' power-operated rolls acting'on the strip during movement through the apparatus for controlling tlie tension of the strip therethrough, whereby a uniform smooth bright surface is provided on the strip.

9. In apparatus for treating an electroplated tin coating on continuous metal strip, means for heating the coating to a fusing temperature, means for thereafter solidifying the` coating, means for continuously moving the strip under tension through the apparatus, and a 'roll acting on the strip during movement through the apparatus in a direction for controlling the tension of the strip therethrough, whereby a' uniform smooth bright tin surface is provided on the strip.

10. In apparatus for treating an electroplated tin coating on continuous metal strip, means for heating the coating to a fusing temperature in one zone, means for thereafter solidifying the coating in another zone, means for continuously moving the strip `under tension, said strip moving means including driven rolls and guide rolls for accumulating a loop in the strip to provide ,for continuous movement of the strip through the heating andsolidifying means during joining of discontinuous lengths of stock to said strip, and a roll acting on the strip i'n a direction,-e1 for controlling the tension of the strip during' of stock to said strip, and power-operated rolls acting on the strip during movement through the apparatus for controlling the tension in the strip therethrough, -whereby a uniform bright tin surface is provided on the strip. i

12. In apparatus for treating electroplated coatings on continuous metal strip, a heating chamber containing a non-oxidizing fluid bath, a cooling chamber containing a non-oxidizing iluid bath.-said cooling chamber being located below and communicating with said heating chamber, means associated with said heatinl chamber for heating the strip to fuse the coating, means associated with said cooling chamber for quickly solidify-ing the coating, means for continuously moving the strip under tension and means for controllingA the tension in the strip through said heating and cooling chambers, whereby a uniform smooth bright tin surface is provided on the strip.

13. In apparatus for treating electroplated coatings on continuous metal strip, means for preheating the strip to a temperature below` the fusing temperature of the coating thereon, separate means for heating the strip for fusing the coating, separate means for cooling-the strip for solidifying the coating, means for continuously moving the strip under tension and means for controlling the tension in the strip through the apparatus, whereby a uniform smooth bright tin surface is provided on the strip; and means for controlling the temperature oi' the strip during preheating, heating and cooling so that the coating is fused for only a short period ot time an'd is quickly solidiiied.

14. In apparatus for treating electro-tin plated coatings on continuous metal strip, means for preheating the strip to a temperature of about 400 F., separate means for heating the strip to a temperature of about 460 F. for fusing the coating, separate means for cooling the strip to a temperature of about 150 F. i'or solidifying the coating, means for continuously moving the strip under tension and means for controlling the tension in the strip through the apparatus, whereby a uniform smooth bright tin surface is provided on thestrip, and means for controlling the temperature of the strip during preheating, heating and cooling so that the coating is fused for only a short period o! time and is quickly solidified.

` JOHN S. NACHTMAN.

REFERENCES crr'En The following references are of record vin the ille of this patent:

UNITED STATES PATENTS Number Name Date '632,836 Douglas Sept. 12, 1899 1,210,663 Mace Jan. 2, 1917 1,355,521 Alexander et al. Oct. 12, 1920 1,517,910 Kirschner Dec. 2, 1924 1,683,129 'Gaisman Sept. 4, 1928 1,811,522 Shover et al June 23, 1931 1,890,065 Meehan Dec. 6, 1932 2,009,856 Otis et al July 30, 1935 2,078,868 Oplinger Apr. 27, 1937 2,141,382 Ferm Dec. 2'7, 1938 2,192,303 Ferm Mar. 5, 1940 2,240,265 Nachtman Apr. 29, 1941 2,357,126 Nachtman Aug. 29, 1944 FOREIGN PATENTS Number Country Date 258,633 Great Britain- Sept. 21, 1926 

